Valve sourcing goes international

Across many types of products in quite a lot of industries, the apply of mixing assorted elements from various resources all over the world is the rule, not the exception. Should this be a priority for a control valve user? For instance, when an finish consumer discovers that several components are being made in China (Figure 1), should the user worry concerning the quality?
When coping with a significant valve vendor, the answer is “no.” There shouldn’t be any room for doubt when the seller has a number of checks and balances in place focusing on product quality to make sure control valves function as designed, want minimal maintenance, carry out safely and function within environmental laws.
Yet, despite such efforts by the seller, a management valve person might have questions about world sourcing and the country of origin. This article discusses how one main management valve vendor ensures product quality. Many other control valve distributors observe the same or comparable procedures.
Quality specification brings world assurance
Emerson enforces a comprehensive high quality specification for its Fisher control valves that have to be met by suppliers of pressure-containing and structural metallic castings. The quality specification includes more than a dozen requirements that apply to the next areas:
Supplier qualification
Welding procedures
Marking inspection and testing
Tryout and pattern castings
Production castings
Certification of compliance
Supplier qualification — Suppliers undergo a rigorous qualification process. The course of thoroughly investigates a potential supplier’s capability to satisfy materials specs and relevant international codes and requirements — as well as particular requirements associated to component manufacture. In the case of castings, a foundry is considered “qualified” when it passes a important evaluation by Fisher’s engineers.
The foundry should demonstrate a document of qualification by a third-party inspection company and conform to various standards, such as ISO 9001:2000, ASME, A2LA, PED and others. It must move a evaluation of its high quality program as nicely as on-site audits of the foundry’s processes and procedures such as welding, warmth treatment and non-destructive examination. Additional proof of efficiency is decided by evaluation of tryout castings to confirm specifications are met.
Welding procedures — Welding is used through the production and upgrading of castings, corresponding to when radiographic examination is required. Welding necessities state that procedures and welder qualifications must meet ASME Section IX (or EN ISO 15614-1 and ISO 9606-1) qualification standards. Similarly, every lot of weld filler must comply with ASME/AWS chemical evaluation specifications. In Europe, compliance must be to EN499. Weld filler will have to have actual chemistry.
Marking inspection and testing — Valve body castings have markings (Figure 2) that identify the foundry that poured the casting and that point out the heat code. Material identification is also usually shown on the body casting, similar to CC, CF8M, CN7M and others.
Casting checks — Emerson technicians conduct both visual inspections and mechanical checks on pressure-retaining castings.
As-cast external and internal surfaces are inspected visually for unacceptable irregularities, including scorching tears and cracks, shrink, sand inclusions, veining and rat tails. Mechanical testing involves a hydrostatic pressure test to verify the leak tightness of a management valve’s pressure-retaining elements, together with the body and bonnet castings. The check process involves a fixture that closes off cavities that may be pressurized in service after which subjects the part to the hydrostatic shell take a look at strain appropriate for the valve body material and sophistication.
ASME B16.34 units out the hydrostatic check stress to use for metal and alloy valves. It’s calculated by multiplying the working stress by 1.5 and rounding to the next greater 25 psig increment. Any visually detectable weeping or leaking by way of the strain boundary walls which would possibly be part of the valve meeting is a mandatory trigger for rejection (Figure 3).
Compliance with these specifications have to be ensured, in addition to with different requirements concerning materials.
Figure 2. Markings establish the foundry and materials of the valve body. These control valve our bodies were cast at an Emerson-approved foundry in China.
Meeting material necessities
Valve casting integrity and quality begins with specifications that call not only for premium supplies, but additionally for the materials that work greatest within the meant applications. These application necessities embrace power and ductility in addition to resistance to sure components, including the makeup of the controlled fluid, working temperature and flow velocity.
For instance, chemical composition have to be controlled precisely to realize an alloy’s intended performance stage. Carbon metal castings for valves meant to be used in oil and fuel functions should meet NACE SP0472 recommendations that chemical composition be controlled to lower than zero.43% carbon equivalency. The decrease carbon content improves weldability and reduces the potential for stress cracking by hydrogen sulfide typically present in oil and gasoline production and processing functions.
Another example of materials tied to a selected software include those for upstream oil and gas production. Many of these applications occur within the arctic areas of Russia and Canada. For this service, castings are ASME SA 352 Grade LCC, while forgings should meet ASME SA 350 Grade LF2.
Many products with international use now adjust to dual material specs to fulfill ASME and European requirements. For example, steel castings are specified and authorized to both ASME SA216 Grade WCC and EN 10213 Grade 1.0619. Emerson usually provides its personal stringent necessities corresponding to the heat treating of high nickel alloys, more demanding chemical composition or special welding procedures.
In the previous, Emerson has supplemented conventional ASTM and ASME specifications to achieve the enhanced corrosion-resistance ranges and high temperature capabilities supplied by high-nickel alloys. This is now achieved by the new ASTM specification A990, which addresses both material composition and high quality.
Figure three. Pressure-retaining elements of a valve are subjected to hydrostatic testing to evaluate the parts’ integrity. Visible leakage or seepage through a casting means automated rejection.
Qualifying a foundry
As part of a potential foundry’s qualification, Emerson inspects and exams Fisher valve castings. Non-destructive testing radiography is used as a monitoring device. ASTM A990 Class C requires radiography of the primary casting of every sample. The acceptance criterion is Level 3 for classes A, B and C. For classes D via G, no cracking, sizzling tears or inserts are allowed as laid out in ASTM A990.
Strange -nickel alloy castings present improved efficiency in corrosive companies and elevated temperatures. However, if high-nickel castings are improperly prepared, they will pose major issues, together with poor integrity, poor weldability and lower-than-expected corrosion resistance. A systematic foundry qualification course of may be adopted to avoid these casting difficulties.
The foundry must solid a 1-inch thick high-nickel test plate (Figure 4) that meets ASTM Material Specification A990. It’s troublesome to cast due to the distinction in cross-section between the base of the weld cavity (in the center) and the general 1-inch thickness of the plate. The cavity of the poured plate is then filled with an identical composition weld materials. The welder and procedure for this step should meet the requirements outlined in Section IX of the ASME Boiler and Pressure Vessel Code. Test bars (3/8-inch thick) are minimize from the plate and bent over a 1½-inch mandrel per ASTM A990 right into a U-shape.
The bars are examined intently for cracking alongside the weld heat-affected zone, casting grain boundaries or dendrite boundaries. Failure to meet quality standards will outcome within the disqualification of the foundry from further consideration. Casting patterns have to be devoted solely to high-nickel alloy service. Use of carbon steel or a stainless-steel pattern is unacceptable because of differences in solidification properties.
Shrinkage rates for gates, risers and different accessories can vary considerably. Once the dedicated sample gear for every of those parts has been secured, try-out castings are poured for each pattern-alloy mixture. The castings are then radiographed.
The intent is to disclose any inherent casting defects — similar to shrinkage — that must be eradicated by modifying the pattern rigging.
Figure four. In a foundry analysis, a casting is filled with weld filler, then sliced to yield a bar for bend testing.
A qualified foundry
Emerson has used a Chinese foundry (Figure 5) to solid Fisher valve our bodies for greater than a decade. After an exploratory go to by procurement and manufacturing specialists, followed by an intensive qualification course of, the foundry was accredited and has been delivering high-quality valve body and bonnet castings to Fisher valve manufacturing websites.
To assist guarantee the quality of the castings it produces, the Chinese foundry has carried out international standards and has obtained certifications for German TUV and CE, Norway DNV, German Lloyd’s and American ABS, and has handed worldwide quality system certifications of ISO 9001 and QS -9000.
The foundry has been awarded Gold Medals thrice consecutively in the Beijing International Casting, Forging and Industrial Boiler Expo. It has twice received an Excellent Supplier award from Emerson.
Figure 5. This Chinese foundry meets all specs for casting valve bodies.
Summary
Control valve customers can be concerned after they study certain valve components aren’t made in the U.S. or Europe, however elsewhere. Perhaps their concern stems from experience with other inferior products, such as appliances, clothes or electronics made in those nations and bought online. But if the valve elements are being provided to a major control valve vendor that has gone to great lengths to qualify the foundry or provider, then customers may be assured the valves meet all specifications.
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